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A comparative study of olivine and clinopyroxene spinifex flows from Alexo, Abitibi greenstone belt, Ontario, Canada

Barnes Sarah-Jane, Gorton M.P. et Naldrett A.J.. (1983). A comparative study of olivine and clinopyroxene spinifex flows from Alexo, Abitibi greenstone belt, Ontario, Canada. Contributions to Mineralogy and Petrology, 83, (3), p. 293-308.

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A petrological and geochemical study of an olivine and of a clinipyroxene spinifex textured flow, from Alexo, indicates that the initial liquid in both flows probably came from the same mantle melting event and that the source was incompatible element depleted. The starting liquid of the clinopyro~ene flow had experienced more olivine fractionation (10%) prior to its emplacement at Alexo, than the initial liquid of the olivine spinifex flow. The development of each of the textural and compositional zones in the flows can be modelled by means of crystal fractionation. In the case of the clinopyroxene flow the B-zone is formed by the fractionation of olivine, low-Ca pyroxene and chromite. An unusual feature of the Alexo clinopyroxene flow is presence of a peridotitic komatiite above the pyroxene cumulate layer, where a basaltic komatiite would usually be present. The presence of the peridotitic komatiite suggests an influx of new magma and hence a dynamic model for the flow. The composition of the clinopyroxene spinifex zone represents a mixture of clinopyroxene plus liquid, rather than simply a frozen liquid. This could happen if the clinopyroxene needles grew stalactitelike from the chilled upper surface of the flow into a flowing basaltic liquid. In the olivine spinifex flow the zones can be modelled as frozen liquids in the A2-zone, as initial liquid which has fractionated 30% olivine in the A3-zone and as liquid plus 50% olivine in the B-zone. But, if the clinopyroxene spinifex developed by stalactite growth of clinopyroxene needles into the a flowing liquid, the possibility that the olivine spinifex represent fractionated liquid plus stalactite olivines arises.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:0010-7999
Volume:83
Numéro:3
Pages:p. 293-308
Version évaluée par les pairs:Oui
Date:1983
Sujets:Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Déposé le:04 juill. 2016 19:31
Dernière modification:09 déc. 2016 15:56
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